Aerodynamic and/or vibrational instabilities, such as but not limited to flutter, can occurs in a gas turbine engine when two or more adjacent blades of a rotor of the engine, such as the fan, vibrate at a frequency close to their natural frequency and the interaction between adjacent blades maintains and/or strengthens such vibration. Other types of aerodynamic instability, such as resonant response, may also occur and are undesirable. Prolonged operation of a rotor undergoing such instabilities can cause airfoil stress loads to exceed acceptable levels for operation.
Various attempts have been made to mistune adjacent blades of such rotors so as to separate their natural frequencies and reduce the likelihood of undesirable instabilities. Continuous improvement is nevertheless sought.